$FreeBSD: releng/11.0/share/examples/kld/khelp/README 218545 2011-02-11 07:26:17Z lstewart $

An example Khelp module which uses the helper hook points available in the TCP
stack to calculate a per-connection count of inbound and outbound packets when
the connection is in the established state. The code is verbosely documented in
an attempt to explain how everything fits together.
